1.8% or 18mg/ml is a decent starting point, but some people need something stronger when they're first switching over from smoking. Most people get about 1 milligram of nicotine from each cigarette, but combustion changes the pH of the nicotine so that it is quickly and easily absorbed in the deep lung tissue. On the other hand, the nicotine in e-cigs is mostly absorbed through the mouth and upper respiratory system so inhaling the vapor into your lungs doesn't really help except to give the "throat hit" you expect from smoking.
Pharmaceutical grade nicotine is also absorbed slower than the nicotine in smoke so some people still find they crave a cigarette in the morning for a jump-start, but I found that after just a few days of one or fewer cigarettes my senses of taste and smell improved enough that I didn't want to smoke at all as long as I can vape instead.
Pharmaceutical grade nicotine is also absorbed slower than the nicotine in smoke so some people still find they crave a cigarette in the morning for a jump-start, but I found that after just a few days of one or fewer cigarettes my senses of taste and smell improved enough that I didn't want to smoke at all as long as I can vape instead.